Here's a strange one. When I run the AC in my '95 LX, I hear a soft, fluttering, whistling noise from somewhere towards the passenger-side dash. I guess it also sounds like a slipping belt, except waaay quieter and waaay less annoying.

The noise is definitely AC-related, and I think it's throttle-related. It comes and goes. Strangely, the noise continues for a few seconds after I turn off the AC, but besides that I never hear the noise when the AC is off.

Any thoughts?

 

ummmm that area is where the evaporator is located. It's fine. Do you have any problems with the A/C?

 

No, the AC seems to work ok, at least as far as I can tell. Since the noise seems to sometimes start and stop with throttle changes, I was thinking that it might be a leaky vacuum motor?

If you're right and it's the evaporator, and the evaporator is fine, then... umm... why wasn't it making this noise before? Could it be something like a stuck or leaky expansion valve that's leaking refrigerant? I guess if it was I wouldn't be getting any cooling...

Is the evap. coil maybe rubbing against something?

 

are you sure its not the compressor? try just turning the fan on without the AC on. The blower motor is located under the glove box. When you shut the fan off, it takes a few seconds to stop turning.....

Also, the evaporator will not make a squeeling noise.

 

Def. not the blower motor. That makes its own noise sometimes. This noise never happens when the AC is off, and I always have the blower on. Changing the blower speed doesn't change the sound any. That doesn't check the compressor, though...

Here's one more detail: I said I can turn off the AC and the noise will continue for a couple sec. I can also kill the engine and get the same thing. That could be a fan spinning down, but I don't think so.


Modified by guymontag at 7:53 PM 8/11/2007

 

Unless there's a separate fan for the evaporator...

 

There is only one fan. If you stick your head near the passenger floor you can see the bottom of the blower motor and the evaporator box. The blower motor is more toward the right. I can't recall if the blower motor has to actually run for the AC compressor to come on, but you could try unplugging the blower motor and turning on the AC. Maybe you can rule out the blower motor. It is possible to have a pinhole leak in the evaporator or other in that area which could create a sort of hissing sound. These years don't have filters for the evaporator so it ends up filling with pine needles and leaves. This makes an acidic situation that corrodes the evaporator and causes leaks.

 

My evap. was swimming in water for a while until I unplugged the drain hole. Thanks for the diagnostic ideas.

 

Did you ever find out what the problem was? Or ever fixed it? Getting the same problem on my 99 Honda Civic LX. ):

 

It's likely it's just the refrigerant passing through the expansion valve. That noise is completely normal. It's a whirling sound. As you accelerate and the rpms climb, the alternator belt spins the ac compressor, which pushes the refrigerant through the system faster. Now if you have water on the floormat that's a different story. If that's happening then it's possible either the drain hose is plugged or the drain hose that attaches to the downward hose is not attached.